This article presents a brief overview of the prevalence, health status, and other characteristics of people with asthma in Australia.

DATA SOURCES

Information for this article is drawn from the ABS 2001 and 2004-05 National Health Surveys, the 2004-05 National Aboriginal and Torres Strait Islander Health Survey, 2004 Causes of Death collection and the 2003 Survey of Disability, Ageing and Carers.

The prevalence of asthma, as measured by the National Health Survey (NHS) is based on people reporting that they had been told by a doctor or nurse they have asthma, and they still get asthma. It should be noted that the 2001 and 2004-05 NHS excluded persons in hospitals, nursing and convalescent homes and hospices and hence the data relates only to persons in private dwellings.

INQUIRIES

For further information about these and related statistics, contact the National Information and Referral Service on 1300 135 070 or email client.services@abs.gov.au.

ASTHMA

Asthma is a chronic inflammatory disease causing episodes of wheezing, breathlessness and chest tightness due to widespread narrowing of the airways within the lungs and obstruction of airflow. Symptoms are more prevalent either at night or in the early morning. The symptoms of an episode are usually reversible, either spontaneously or with treatment (AIHW 2006a).

PREVALENCE

In 2004-05, after adjusting for age differences, 10% of people in Australia reported that they had asthma. This is a slight decrease from the rate in 2001 (12%) (footnote 1).

In 2004-05, there were approximately 2 million (10%) people in Australia who reported asthma as a current long term condition.

During the early 1990s, the International Study of Asthma and Allergies in Childhood (ISAAC 1995) found that Australia ranked third (out of 44 participating countries) for the prevalence of self-reported wheeze among children aged 13-14 years in the last 12 months. A similar study of adults aged 20-44 years found that Australia ranked second (out of 41 countries) in terms of prevalence of self-reported wheeze in the last 12 months (GINA 2004).

AGE AND SEX

Asthma is the most common chronic illness in children (Telethon Institute for Child Health Research).

In 2004-05, asthma was the most commonly reported long-term condition for children aged 0-14 years (12%). Asthma was also common among young adults (12% for those aged 15-24 years).

Among people aged 25 years and over, the prevalence of asthma was just over 9%.

In 2004-05, asthma was more prevalent in females (11%) than in males (9%).

Asthma prevalence peaked at a much earlier age for males (10-14 years) than for females (20-24 years). Of children aged 0-14 years, boys were more likely to have asthma than girls (13% compared with 10%). After 15 years of age, females were more likely than males to report having asthma (12% of females compared with 8% of males).

Prevalence of asthma, 2004-05

INDIGENOUS AUSTRALIANS

In 2004-05, 15% of Indigenous Australians reported that they had asthma as a current or long term condition (ABS 2006d).

After adjusting for age differences between the two populations, Indigenous Australians were one and a half times as likely as non-Indigenous Australians to report having asthma (16% compared with 10%) (ABS 2006d).

In 2004-05, asthma was most prevalent for Indigenous people aged 45 years and over. 19% of Indigenous Australians aged 45 years and over reported that they had asthma compared with 9% of non-Indigenous Australians in the same age group (ABS 2006d).

The pattern of prevalence was different for non-Indigenous and Indigenous Australians. Asthma prevalence peaked at a later age for Indigenous people (45 years and over) than for non-Indigenous people (15-24 years) (ABS 2006d).

Prevalence of asthma among Indigenous and non-Indigenous Australians, 2004-05

HEALTH STATUS

People with asthma rate their health lower, have a higher prevalence of psychological distress and a greater proportion of those with asthma reported having days away from work or study in the last two weeks than those without asthma (AIHW 2005).

In 2004-05, after adjusting for age differences, adults with asthma were more likely to rate their health as poor (8%) than people without asthma (3%), and less likely to report their health as excellent (7% compared with 13%).

In 2004-05, 14% of people with asthma (274,000 people) also reported having a mental or behavioural problem, compared to 12%of people without asthma.

Adults with asthma tended to report higher levels of psychological distress (footnote 2)than those without asthma in 2004-05. Of people aged 18 years and over with asthma, 5% had very high and 9% had high levels of psychological distress, with a further 18% being classified at a moderate level and 34% at a low level of psychological distress, (age-adjusted). This compares to those without asthma, where there were 2% with very high and 5% with high levels of psychological distress (and 15% at moderate and 43% at low levels).

In 2004-05, adults (15 years and over) with asthma were more likely to report having days away from work or study (10%) than adults without asthma (7%), age adjusted. Children aged 5-14 years with asthma were more likely to report having days away from study (22%) than children without asthma (14%), age adjusted.

Two different studies, the NSW Health Survey in 1997 (Marks et al. 2000) and an assessment of the supplementary asthma module of the Bettering the Evaluation and Care of Health (BEACH) general practice survey between 1999 and 2003 found that approximately one-third to one-half of adults with asthma have moderate or severe disease(footnote 3)(AIHW GPSU 2000, 2001, 2003, 2004, Henderson et al. 2004).

Arthritis was also more commonly reported by people with asthma (20% or just over 402,000 people) in 2004-05, compared with those without asthma (17%).

DISABILITY

In 2003, about 149,000 people (4% of all people with a disability) reported that asthma was the main condition causing their disability. Of these people, 32,400 (22%) had a profound or severe limitation with the core activities of communication, mobility or self care (footnote 4)(ABS 2004).

The most common disabilities that people with asthma reported in 2003 were restrictions in physical activities or work (46%) and breathing difficulties (37%) (ABS 2004a).

COUNTRY OF BIRTH

People from non-English speaking backgrounds have a lower prevalence of asthma than those from English speaking backgrounds (AIHW 2005).

In 2004-05, after adjusting for age differences, the highest prevalence rates of asthma were for people born in Australia (11%), other parts of Oceania (10%) and the United Kingdom (9%). The lowest prevalence rates were for people born in North Africa and the Middle East and Southern and Eastern Europe (5%).

Asthma prevalence rates have been found to increase among migrant populations the longer their duration of residence in Australia (Leung et al. 1994).

RISK FACTORS

There are several recognised risk factors that increase a persons chance of developing asthma or triggering symptoms in people who already have the condition. These factors include constitutional factors such as age, sex and family predisposition and environmental and related factors such as diet and lifestyle (AIHW 2005).

There are a number of factors which may trigger symptoms in people who already have the condition including exercise, viral infections, irritants (including smoking and indoor and outdoor air pollutants), specific allergens (eg dust mites and mould spores) and certain ingested food preservatives. In most cases, except for viral infections and air pollutants, simply by avoiding exposure to these factors will prevent or control symptoms in people with asthma (AIHW 2005).

In 2004-05, after adjusting for age differences, the proportion of people with asthma who did not eat the recommended daily intake of fruit (33%) was significantly greater than the proportion of people without asthma (29%).

Tobacco Smoking

The adverse effects of active and passive smoking on the general public are well known and people with asthma who smoke have additional morbidity. Smokers with asthma have more symptoms, worse asthma control (Siroux et al. 2000), an accelerated decline in lung function (Lange et al. 1998), more airway inflammation (Chalmers et al. 2001), and a less beneficial response to inhaled corticosteroid treatment (Chalmers et al. 2002; Pedersen et al. 1996) compared with non-smokers with asthma (AIHW 2005).

In 2004-05, the proportion of current daily smokers among people aged 18 years and over with asthma (24%) was slightly higher than the proportion of current daily smokers without asthma (21%).

Among people with asthma, those who are younger and live in localities that are relatively socioeconomically disadvantaged are more likely to smoke (AIHW 2005).

Exposure to environmental tobacco smoke in childhood is a recognised risk factor for the development of asthma symptoms and also for the worsening of pre-existing asthma (AIHW 2005).

There is a higher rate of household exposure to smokers among children with asthma (AIHW 2005).

In 2004-05, 40% of children aged 0-14 years with asthma lived with one or more smokers in their household compared with 36% of children without asthma. This is most evident in girls aged 0-4 and 10-14 years and boys aged 5-14 years and people living in more socioeconomically disadvantaged areas.

MANAGEMENT

Research has shown that preventers (inhaled corticosteroids) are effective in controlling the symptoms of asthma and in preventing complications (Rowe et al. 2000).

In 2004-05, 55% of people with asthma used pharmaceutical medications to prevent and/or relieve their asthma symptoms. In 2004-05, 85% of people with asthma had used a reliever in the last two weeks (footnote 5), and 39% of people with asthma had used preventers in the last two weeks(footnote 6).

It is well established that respiratory infections can worsen asthma symptoms by acting as triggers for an attack (Dell et al 2001). People aged 50 years and over with asthma were more likely to have had an influenza (61%), or pneumococcus (35%) vaccination than people of the same age without asthma (45% and 19% respectively). (In 2004-05, only those aged 50 years and over were asked to report whether they had ever had a flu injection or flu shot.)

Asthma action plans (AAPs) have formed part of national guidelines for the management of asthma since 1989 (National Asthma Campaign 1998). In 2004-05, 16% of people with asthma reported having a standard AAP. Children aged 0-14 years with asthma were more likely to have a standard AAP (26%) than adults with asthma (14%).

In 2004-05, after adjusting for age differences, 24% of people with asthma had recently (in the last two weeks) consulted a GP or specialist compared to 17% of people without asthma. Also, 5% of people with asthma had recently been discharged from hospital or had visited outpatients, attended the emergency department or visited a day clinic compared with 4% of people without asthma.

MORTALITY

In 2004, there were 313 deaths (108 males and 205 females) where asthma and acute severe asthma were identified as the underlying cause. Asthma was the underlying cause of death for 0.2% of all deaths (132,508) in that year (ABS 2006b). Asthma was also mentioned as an associated cause of death in a further 895 reported deaths in 2004 (ABS 2006b).

In 2004, the most common associated causes of death for people with asthma were influenza and pneumonia (84 cases) and ischaemic heart disease (56 cases) (ABS 2006c).

Although the prevalence of asthma is high among children, the risk of dying from asthma increases with age. In 2004, 195 deaths from asthma occurred in people aged 70 years and over, which represented 62% of deaths from asthma in that year (AIHW 2005). Older people are also at greater risk of dying from asthma during winter (AIHW 2005).

Death rates for asthma have been declining since 1997. In 1997, the age standardised death rate for asthma was 2.7 per 100,000 for males and 3.0 per 100,000 for females compared with 1.2 per 100,000 for males and 1.7 per 100,000 for females in 2004 (ABS 2006b).

In a study conducted in 2004, Australia was ranked 22nd out of 67 countries for the mortality of people aged 5-34 years (per 100,000 population) due to asthma, which is moderately high by international standards (GINA 2004).

Trends in asthma mortality, 1997-2004

HOSPITALISATIONS

In 2004-05, asthma and acute severe asthma (footnote 7)accounted for 37,461 hospital separations. Children aged 0-14 years accounted for just over 50% of these (AIHW 2006).

Among children, boys have higher rates of hospitalisation for asthma than girls, which is in keeping with the higher prevalence of asthma in boys. However this trend is reversed after the age of 15 years when more females than males are admitted to hospital for asthma (AIHW 2005).

Children aged 0-4 years have the highest rate of emergency department visits for asthma, while children aged 0-4 years and people aged 65 years and over are most likely to be admitted to hospital for asthma after going to an emergency department for treatment (AIHW 2005). During the period July 1999 to June 2004 in NSW and Victoria, 48% of boys and 47% of girls aged 0-4 years with asthma were admitted to hospital following a visit to an emergency department while for those aged 65 years and over 57% of males and 65% of females with asthma were admitted to hospital following a visit to an emergency department. Overall, among those with asthma visiting an emergency department for treatment of their asthma symptoms, 88% of patients who were triaged under the 'resuscitation' category (footnote 8)were admitted to hospital (NSW Department of Health & Victorian Department of Human Services).

Among people aged 65 years and over, hospitalisation rates for people with asthma are highest during the winter months, while for children with asthma, hospitalisation rates are higher during late summer and autumn (AIHW 2005).

HEALTH SYSTEM COSTS

In 2000-01, health expenditure on asthma was $693 million, which represents 1.4% of total health expenditure for Australians for that year (AIHW 2005).

FOOTNOTES

1. Since many health characteristics are age-related, the age profile of the populations being compared needs to be considered when interpreting the data. To account for the differences in age structure, much of the comparative data contained within this publication are shown as age standardised percentages. For further detail, see the Explanatory Notes of the National Health Survey: Summary of Results, 2004–05 (cat. no. 4364.0). Back

2. The Kessler Psychological Distress Scale - 10 (K10) is used as a measure of non-specific psychological distress. A very high level of psychological distress, as shown by the K10, may indicate a need for professional help. In the 2004-05 NHS, the K10 questions were asked of adults aged 18 years and over. For more information, see Australian Bureau of Statistics Information Paper: Use of Kessler Psychological Distress Scale in ABS Health Surveys, 2003 (cat. no. 4817.0.55.001). Back

3. Severity of asthma is graded according to the presence of a number of symptoms including wheezing, coughing, sleeping patterns, history of previous attacks, hospital admissions, use of bronchodilators and other indicators within a specified timeframe (usually a day or week) (AIHW 2005 pp 153-154). Back

4. The four levels of core-activity limitation are determined based on whether a person needs help, has difficulty, or uses aids and equipment with any of the core activities of communication, mobility or self care. A person's overall level of core-activity limitation is determined by their highest level of limitation in these activities (ABS 2004).Back

5. Relievers - are usually in blue/grey delivery devices. They provide immediate relief from asthma symptoms by relaxing muscles around the airways. If they are used more than three or four times a week (except for controlling exercise-induced asthma), you should speak to your doctor, as this may indicate that the asthma is not well controlled. This is the only medication to use in an asthma attack.Back

6. Preventers - are usually in brown, white, yellow or orange delivery devices. Preventers make the airways less sensitive to triggers and reduce swelling and redness (inflammation) inside the airways. They are taken daily to keep you well. Do not stop taking the preventer, even when you are feeling better.Back

7. Asthma and acute severe asthma are classified according to the International Classification of Diseases, Tenth Revision, (ICD-10) codes J45 and J46. Back

8. When people present to an emergency department for treatment they are assessed and assigned a triage category, based on their condition, that designates the maximum permissible waiting time. There are five levels of triage category and waiting times: 1 Resuscitation (within 1 minute); 2 Emergency (within 10 minutes); 3 Urgent (within 30 minutes); 4 Semi-urgent (within 60 minutes); and 5 Non-urgent (within 120 minutes). Back

ISAAC (International Study of Asthma and Allergies in Childhood) Steering Committee 1995. International study of asthma and allergies in childhood (ISAAC): rationale and methods. European Respiratory Journal 8:483–91.

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